The present invention relates to a ceramic electronic component including external electrodes and to a method of producing the ceramic electronic component.
Along with use of lead-free electronic devices, there have also been demands for use of lead-free ceramic electronic components mounted to those electronic devices. Further, there has been another demand to improve mountability of the ceramic electronic components with use of tin-based lead-free solder. In order to meet such demands, it is effective to use the outermost layer of an external electrode of the ceramic electronic component as a tin layer.
An external electrode of a general ceramic electronic component includes a copper layer. However, it is known that the external electrode, in which a tin layer is formed on the copper layer, is likely to generate whiskers that grow like hairs from the tin layer. When the whiskers are separated from the tin layer and drop on a circuit board, this will be a cause of a short circuit of the circuit board.
It is thought that whiskers are generated when compressive stress is applied to the tin layer. In this regard, in the external electrode, an intermetallic compound containing tin and copper is likely to be generated at a boundary portion between the tin layer and the copper layer. The volume of such an intermetallic compound increases when generated, and thus the intermetallic compound applies compressive stress to the tin layer. It is thought that the above fact causes the generation of the whiskers in the tin layer.
WO 2013/111625 and Japanese Patent Application Laid-open No. 2013-91848 each disclose a technique capable of suppressing the generation of the whiskers in the tin layer. In the techniques disclosed in WO 2013/111625 and Japanese Patent Application Laid-open No. 2013-91848, a nickel layer is provided between the tin layer and the copper layer. With this configuration, the nickel layer hinders the tin layer and the copper layer from coming into contact with each other, and thus an intermetallic compound containing tin and copper can be prevented from being formed.